1. Field of the Invention
The invention relates to wool fat alone or in combination with oil-soluble auxiliary flow-improving material whereby the cold flow properties of middle distillate fuel oil are improved.
2. Description of the Prior Art
Kerosene, which is a solvent for wax, has traditionally been a component of middle distillate fuel oils, e.g. diesel fuels, home heating oils, etc. With the demands for kerosene for use in jet fuels, the amount of kerosene used in distillate fuel oils have decreased over the years. This, in turn, has frequently required the addition of wax crystal modifiers, e.g. pour point depressant additives, to the fuel oil to make up the lack of kerosene.
Included in the auxiliary flow-improving compounds are a class of lubricating oil pour point depressant additives, namely, alkylated aromatics, particularly the wax-naphthalene pour point depressants. These materials have been used in various petroleum oils, such as lubricating oils, e.g. see U.S. Pat. Nos. 1,815,022 and 2,297,292; as dewaxing aids, including use with other co-additives, e.g. see U.S. Pat. Nos. 3,417,010 and 3,475,321; and as pour depressants for middle distillate fuels, e.g. see U.S. Pat. No. 3,245,366.
A group of distillate fuel oil pour depressants are the copolymers of ethylene with various other monomers, e.g. copolymers of ethylene and vinyl esters of lower fatty acids such as vinyl acetate (U.S. Pat. No. 3,048,479); copolymers of ethylene and alkyl acrylate (Canadian Pat. No. 676,875); terpolymers of ethylene with vinyl esters and alkyl fumarates (U.S. Pat. Nos. 3,304,261 and 3,341,309); polymers of ethylene with other lower olefins, or homopolymers of ethylene (British Pat. Nos. 848,777 and 993,744); chlorinated polyethylene (Belgium Pat. Nos. 707,371 and U.S. Pat. No. 3,337,313); etc.
Wool fat has been added to hydrocarbon oils such as those originating from paraffin base crude petroleum and obtained by hydrogenation to appreciably reduce the pour point of such oils (U.S. Pat. No. 2,023,369). Lanolin or wool grease are taught to be capable of improving the filter rate of hydrocarbon oils and reducing the oil content of the wax cake in dewaxing operations (U.S. Pat. No. 2,099,190 and 2,209,168). Lubricating oil pour point depressants and dewaxing aids of hydrocarbon oils are generally found to exhibit little to no flow improving activity in middle distillate fuels.
U.S. Pat. No. 3,762,888 teaches improving the cold flow properties of middle distillate fuels with a combination of oil-soluble, pour point depressant polymers together with oil-soluble auxiliary, flow-improving compounds.